The Barkley Marathons, held every year in the rugged hill country of Tennessee, pit runners against their absolute mental and physical limits. The race is five 20-mile loops, almost entirely off-trail, with a total elevation gain that more than doubles the height of Mt. Everest. In three decades, only 14 people have ever finished.

A 60-hour time limit forces competitors to run, climb and bushwhack for three days with little or no sleep. They endure taunts from the race director, who deliberately keeps the competition’s entry procedure a mystery. It is a race in which there are no comfort stations, and runners cannot use a GPS device or a cellphone. Less than 2 percent of the nearly 800 ultrarunners who have subjected themselves to this punishment — 12 men, the same number as have walked on the moon — have finished the race in its current iteration. The only prize is that after 100 miles, they get to stop.

At least they don’t have to pay too much to be among the many who fail. The race costs less than $2 to enter. Still, for something that sounds so awful, wouldn’t you think someone would have to pay you?